5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> [ Upstream commit f43c283a89a7dc531a47d4b1e001503cf3dc3234 ] Use the helper fget_task and simplify the code. As well as simplifying the code this removes one unnecessary increment of struct files_struct. This unnecessary increment of files_struct.count can result in exec unnecessarily unsharing files_struct and breaking posix locks, and it can result in fget_light having to fallback to fget reducing performance. Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx> Reviewed-by: Cyrill Gorcunov <gorcunov@xxxxxxxxx> v1: https://lkml.kernel.org/r/20200817220425.9389-4-ebiederm@xxxxxxxxxxxx Link: https://lkml.kernel.org/r/20201120231441.29911-4-ebiederm@xxxxxxxxxxxx Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- kernel/kcmp.c | 20 ++++---------------- 1 file changed, 4 insertions(+), 16 deletions(-) diff --git a/kernel/kcmp.c b/kernel/kcmp.c index c0d2ad9b4705d..bd6f9edf98fd3 100644 --- a/kernel/kcmp.c +++ b/kernel/kcmp.c @@ -107,7 +107,6 @@ static int kcmp_epoll_target(struct task_struct *task1, { struct file *filp, *filp_epoll, *filp_tgt; struct kcmp_epoll_slot slot; - struct files_struct *files; if (copy_from_user(&slot, uslot, sizeof(slot))) return -EFAULT; @@ -116,23 +115,12 @@ static int kcmp_epoll_target(struct task_struct *task1, if (!filp) return -EBADF; - files = get_files_struct(task2); - if (!files) + filp_epoll = fget_task(task2, slot.efd); + if (!filp_epoll) return -EBADF; - spin_lock(&files->file_lock); - filp_epoll = fcheck_files(files, slot.efd); - if (filp_epoll) - get_file(filp_epoll); - else - filp_tgt = ERR_PTR(-EBADF); - spin_unlock(&files->file_lock); - put_files_struct(files); - - if (filp_epoll) { - filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff); - fput(filp_epoll); - } + filp_tgt = get_epoll_tfile_raw_ptr(filp_epoll, slot.tfd, slot.toff); + fput(filp_epoll); if (IS_ERR(filp_tgt)) return PTR_ERR(filp_tgt); -- 2.43.0
